From the Guidelines
For a patient presenting with bruising, a complete blood count (CBC) and coagulation studies including prothrombin time (PT), partial thromboplastin time (PTT), and international normalized ratio (INR) should be ordered first to evaluate the underlying cause. These initial tests can help identify potential thrombocytopenia, bone marrow disorders, or clotting cascade dysfunction.
Initial Evaluation
- A CBC is essential to assess platelet count and identify potential thrombocytopenia or bone marrow disorders 1.
- Coagulation studies, including PT, PTT, and INR, are crucial to evaluate the clotting cascade function 1.
Additional Tests
- Specific factor assays may be needed if a factor deficiency is suspected, particularly Factor VIII and IX for hemophilia 1.
- Liver function tests should be included since liver disease can impair clotting factor production 1.
- Von Willebrand factor antigen and activity tests are important if von Willebrand disease is suspected 1.
- A peripheral blood smear can help identify abnormal platelet morphology or other cellular abnormalities 1.
Special Considerations
- For patients with unexplained or severe bruising, additional tests might include fibrinogen levels, D-dimer, fibrin degradation products, and platelet function tests 1.
- These tests help distinguish between disorders of primary hemostasis (platelet-related) and secondary hemostasis (coagulation factor-related), allowing for appropriate diagnosis and management of the underlying condition causing the bruising. It's worth noting that while the provided evidence includes studies from 2013 1, the most recent and relevant study for guiding laboratory tests in the context of bruising is from 2021 1, which emphasizes the importance of a thorough initial evaluation including CBC, coagulation studies, and assessment of liver function and specific factor deficiencies as needed.
From the Research
Laboratory Tests for Bruising
The following laboratory tests can be ordered for a patient presenting with bruising:
- Complete blood count (CBC) 2, 3, 4
- Peripheral blood smear 2, 3, 4
- Prothrombin time (PT) 2, 3, 4, 5, 6
- Partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT) 2, 3, 4, 5, 6
- Fibrinogen 4
- Bleeding time (BT) 5, 6
- Vitamin K challenge 2
- Liver function tests (if liver failure is suspected) 2
- Factor VIII assay 3
- Von Willebrand factor antigen 3
- Von Willebrand factor activity (ristocetin cofactor assay) 3
- Template bleeding time 3
- Multimeric analysis of von Willebrand factor 3
Interpretation of Laboratory Results
Abnormal results from these tests may indicate a bleeding disorder, such as:
- Platelet disorder (e.g., von Willebrand disease) 2, 3, 4
- Coagulopathy (e.g., hemophilia) 2, 3
- Liver disease 2
- Vitamin K deficiency 2
- Disseminated intravascular coagulation 6
Further Evaluation
If initial testing does not reveal an etiology in a patient with a high suspicion for a bleeding disorder, the patient should be referred to a hematologist for additional evaluation 2, 4.